Published research has correlated significant adverse consequences such as impaired wound healing, adverse cardiac events, altered drug metabolism, and coagulopathies with unplanned perioptive hypothermia. With prevention, and management of hypothermia, patients also experience a greater level of comfort, and avoid postoperative shivering and the unpleasant sensation of feeling cold.
The warming of infusate or intravenous (IV) fluids to prevent hypothermia in the current state of the art is accomplished by many varied systems. One such system, the Ranger Fluid Warmer from Arizant Healthcare, uses two heated plates with bladder-like plastic membrane containing a serpentine fluid path held between the plates to heat the infusate through the bladder wall by contact heat transfer. A second such system is disclosed in U.S. Pat. No. 4,532,414. The '414 system uses a box-like enclosure that contains a heated plate with a serpentine groove into which an infusate lumen or conduit is placed. When the box is closed, the infusate is heated by heat transfer from the warm plate through the lumen wall. A third such system is disclosed in U.S. Pat. No. 5,063,994 assigned to the assignee of the instant invention. The '994 system uses a triple lumen tube with warm water being circulated through the two outer lumens to warm the infusate in the central lumen through heat transfer. These systems are all heat transfer systems whereby various types of heat exchangers are used with disposable heat exchanging mediums.
The heat exchanger type infusate warmers in the prior art all have a common drawback. This is because heat exchangers, as their name implies, exchange heat through a heat exchange medium. Thus, there is a time lag in the heat being transferred from the heating element to the infusate or fluid (and removed therefrom), as there is a partition in the form of a wall or membrane that separates the heating element and the medium that is being heated and which tends to stay warm even after it is no loner being heated by the heating element. A need therefore exists for a system that can provide substantially instantaneous control of the heating of an infusate or intravenous fluids.